FLOWER DAMAGE IN CONTRASTING HABITATS 503 REVISTA CHILENA DE HISTORIA NATURAL Revista Chilena de Historia Natural 85: 503-511, 2012 © Sociedad de Biología de Chile RESEARCH ARTICLE Reproductive consequences of fl ower damage in two contrasting habitats: The case of Viola portalesia (Violaceae) in Chile Consecuencias reproductivas del daño fl oral en dos hábitats contrastantes: el caso de Viola portalesia (Violaceae) en Chile CLAUDIA L. ESPINOZA, MAUREEN MURÚA, RAMIRO O. BUSTAMANTE, VÍCTOR H. MARÍN & RODRIGO MEDEL* 1Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, Casilla 653, Santiago, Chile *Corresponding author: [email protected] ABSTRACT The indirect impact of fl ower herbivory on plant reproduction depends on the pollination environment, particularly on the presence or absence of pollinator species with the ability to discriminate damaged from undamaged fl owers. The change in pollinator assemblages, due to habitat modifi cation, may modify the impact of fl ower herbivory on plant reproductive success. In this work, we evaluate the effect of fl ower herbivory on the seed production of Viola portalesia (Gay) in two contrasting environments, a native and low-disturbed habitat and an extensively transformed habitat characterized by Pinus radiata plantations. Even though the two habitats differed substantially in the composition of pollinator assemblages and visitation rate, the fl ower damage performed on different petals had no impact on seed production neither within nor between habitats, indicating that change in pollinator assemblages have no indirect reproductive impact via discrimination of damaged fl owers. There was a strong habitat effect, however, for seed production, being higher in the pine plantation than in the native habitat. Seed production on a per fl ower basis increased at a higher rate with the number of fl owers in the pine plantation, which suggests a numerical response of pollinators to changes in food availability in this habitat. Key words: fl ower herbivory, habitat loss, Maulino forest, Pinus radiata, pollination. RESUMEN El impacto indirecto de la herbivoría fl oral sobre la reproducción de las plantas puede depender del ambiente de polinización, particularmente de la presencia o ausencia de especies de polinizadores con capacidad de discriminar entre las fl ores dañadas y no dañadas. El cambio en el ensamble de polinizadores, debido a la modifi cación del hábitat, puede alterar el impacto de la herbivoría fl oral sobre el éxito reproductivo de las plantas. En este trabajo, se evaluó el efecto de la herbivoría fl oral sobre la producción de semillas de Viola portalesia (Gay) en dos ambientes contrastantes, un hábitat nativo, con bajos niveles de perturbación y otro hábitat altamente intervenido por plantaciones de Pinus radiata. Aún cuando los dos hábitats difi rieron substancialmente en la composición del ensamble de polinizadores y tasas de visitas, el daño fl oral realizado sobre los diferentes pétalos no tuvo efectos sobre la producción de semillas ni dentro ni entre hábitats, indicando que el cambio en el ensamble de polinizadores no tiene impacto reproductivo a través de la discriminación de fl ores dañadas. Se observó, sin embargo, un fuerte efecto del hábitat sobre la producción de semillas siendo ésta mayor en la plantación de pino que en el hábitat nativo. La producción de semillas por fl or relativa al número de fl ores aumentó a una mayor tasa en la plantación de pino, lo cual sugiere una respuesta numérica de los polinizadores a cambios en la disponibilidad de alimento en este hábitat. Palabras clave: bosque Maulino, herbivoría fl oral, pérdida de hábitat, Pinus radiata, polinización. INTRODUCTION (McCall & Irwin 2006). In general, flower herbivory may have a direct impact The impact of flower herbivory on plant on reproductive success by damaging the reproductive success may vary from strong negative effects (Mothershead & Marquis reproductive structure of fl owers and also an 2000) to neutral effects (Malo et al. 2001), indirect effect on reproduction by altering depending on the pollination environment the flower characters involved in pollinator 504 ESPINOZA ET AL. attraction (e.g., Herrera et al. 2002, McCall information on the potential density-dependent & Irwin 2006, Pohl et al. 2006). For example, effects on plant fi tness. More specifi cally, we fl ower herbivory has been shown to infl uence will attempt to answer the following questions: the quality and quantity of diverse flower 1) Do native and pine plantation habitats differ traits such as petal size (Mothershead & in the composition of pollinator assemblages? Marquis 2000), nectar production (Krupnick 2) Does fl ower damage affect seed production & Weis 1999), fl ower production (Lohman et in native and pine plantation habitats? 3) To al. 1996, McCall & Irwin 2006) and fl owering what extent, variation in seed production time (Frazee & Marquis 1994), all characters can be ascribed to changes in the pollination that influence pollinator attraction and the environment between habitats? These questions quality and quantity of pollination service relate to a more general, 4) Do differences exist (Cunningham 1995, Krupnick & Weis 1999, in the indirect impact of fl ower damage on plant Mothershead & Marquis 2000). The most reproductive success between the native and obvious consequence of a reduction or loss modifi ed habitat? of pollination service is the reduction in fruit set and seed set (e.g., Aguilar & Galetto METHODS 2004, Aguilar et al. 2006). Notwithstanding, pollinator species often differ in their ability Viola portalesia (Violaceae) is an endemic self- incompatible herb species that distributes along the to distinguish damaged from undamaged Costal Range in central Chile. Its fl owering season spans fl owers (Schaefer et al. 2004), which suggests from September - November, after which a trivalve fruit the fi nal outcome of fl ower herbivory may be is produced. Viola portalesia inhabits indistinctly natural and pine plantation habitats in the Maulino forest, contingent to the composition of the pollinator a natural forest that has been extensively subject to assemblage (Pohl et al. 2006). One of the human-induced alteration, mainly through deforestation most conspicuous effects of habitat loss is the and subsequent replacement of the native forest by plantations of Pinus radiata D. Don (Bustamante et al. alteration in the composition and abundance 2003). This practice has produced a highly fragmented of pollinator assemblages, as well as the landscape of native habitat embedded in a matrix of behavioral change of particular pollinator Pinus that leads to an ample variation in the abundance and species richness of diverse functional groups (Grez species (e.g., Didham et al. 1996, Thomas et et al. 2006). al. 2001, Goverde et al. 2002). Less obvious are Fieldwork was performed in two contrasting effects on pollination service caused by habitat populations of Los Ruiles National Reserve and surrounding areas from October 2007 to January 2008, modifi cation that propagate indirectly to plant thereby covering the complete flowering season of reproduction through changes in the response V. portalesia. The fi rst population was located within of pollinator assemblages to fl ower damage. the National Reserve (35°83’ S; 72°50’ W). The most representative species at the Reserve are Nothofagus If habitat change modifies the composition alessandri, Nothofagus glauca, Ugni molinae, Oxalis and abundance of pollinator assemblages it articulata, Teline monspessulana, and Viola portalesia. is likely that the effect of fl ower damage in The second population was embedded in a matrix of Pinus radiata located 3.6 km from the fi rst population reducing pollinator service depends on the (35°85’ S; 72°46’ W). The Pinus plantation was 20- presence or absence of particular pollinator year old, and had an understory with a low herb and species sensitive to habitat alteration. While shrub species richness that included Azara integrifolia, Lithraea caustica, Ugni molinae and Viola portalesia as many studies have examined the effect of the most representative species. habitat change on the composition of pollinator We performed experimental damage on 63 plants assemblages (e.g., Rathcke and Jules 1993, in the National Reserve and 59 plants in the Pinus plantation. Only plants with at least four fl ower buds Murcia 1996, Cunningham 2000, Aizen & were chosen. As pollinators may respond to the fl ower Feinsinger 2004, Murúa et al. 2010), to our number in the neighborhood of the focal plant of V. knowledge evidence for an indirect role of portalesia, we recorded the number of flowers in a circular area 2 m diameter around the focal plant. The habitat change on fl ower herbivory and plant number of fl owers per patch ranged between 1-110 in reproductive success is lacking. the native forest and 1-115 fl owers in the pine plantation The aim of this study is to examine the habitat. We allocated 1-day flowers to one of four treatments per plant: 1) removal of the landing petal, effect of fl ower damage on the reproductive 2) removal of the lower petals, 3) removal of the upper success of Viola portalesia in contrasting petals, and 4) control fl ower without damage (Fig. 1). habitats of the Maulino forest. We will also The total area of the petals removed was kept as constant as possible in all treatments. In addition to experimental evaluate the impact of floral damage as a treatments, we estimated the frequency of natural fl ower function of fl ower density, which will provide herbivory by recording the number of fl owers damaged FLOWER DAMAGE IN CONTRASTING HABITATS 505 Fig. 1: Description of treatments applied to petals of Viola portalesia. A) Removal of the landing petal (T1), B) removal of the lateral petals (T2), C) removal of the upper petals (T3), D) control without petal removal (T4). Descripción de los tratamientos aplicados a los pétalos de Viola portalesia. A) Remoción del pétalo de aterrizaje (T1), B) remo- ción de los pétalos laterales (T2), C) remoción de los pétalos superiores (T3), D) control sin remoción de pétalos (T4).